The present invention generally relates to electrodes and, more particularly, electrodes suitable for transcutaneous nerve and/or muscle stimulation and biological signal recording.
Medical electrodes must provide an even electrical coupling to a patient""s skin over an entire surface of the electrode to effect proper coupling. Because of the curvaceous nature of the human body, it is apparent that medical electrodes for use thereon must be flexible not only for confirmation with a patient""s skin contours, but also to accommodate relative movement of the patient""s skin.
It is well known that inadequate flexing and shaping of the electrode to a patient""s contour can result in an irritation of the patient""s skin. Electrical xe2x80x9chot spotsxe2x80x9d due to uneven electrode-skin contact can result in a rash or a burning sensation. A sensation of burning may be felt by a patient within a few minutes after application of the electrical signals during nerve and/or muscle stimulation, while rash conditions generally take a longer period of time to develop.
In order to provide uniform electrical coupling, heretofore developed electrodes have utilized conductive fabrics and foils in combination with a conductive adhesive in order to uniformly couple electrical signals to and/or firm an electrical lead wire, or connector. A number of electrodes have provided impedance compensation for directing electrical pulses from the lead wire uniformly throughout an electrode, such as, for example, U.S. Pat. No. 5,038,796 entitled, ELECTRICAL STIMULATION ELECTRODE WITH IMPEDANCE COMPENSATION, to Axelgaard. This patent teaches the use of an electrical shunt interconnected with the lead wire for causing more uniform resistance between equally spaced apart points in the electrode.
Without this shunt, many prior art electrodes have compromised the flexibility of the electrode in order to provide adequate current densities over the entire contact area of the electrode. These electrodes typically have utilized a metallic mesh, or foil, to provide conductivity and utilize a conductive gel between the electrode and the patient""s skin in order to accommodate the movement therebetween. Contact between the lead wire and the metallic mesh, or foil, is typically a point contact. Because of this, electrode contacts to medical electrodes have typically been made on a top side thereof, that is, a side opposite a side of the electrode having a conductive adhesive thereon for application to a patient.
The present invention is directed to a medical electrode having an intermediate connector, that is, a connector disposed between the conductive member and the conductive adhesive which provides yet another method for controlling the current density provided by the electrode.
A medical electrode in accordance with the present invention generally includes a conductive flexible member having a top side and a bottom side and a non-conductive flexible sheet covering the conductive flexible member top side.
A connector is provided in contact with the conductive flexible member bottom side for establishing electrical contact with external electrical apparatus.
A conductive hydrogel adhesive disposed on the conductive flexible member bottom side for adhering the electrode to a patient""s skin. More particularly, the medical electrode may include a snap eyelet having a head in contact with the conductive flexible member and a shaft extending through the flexible member and a non-conductive flexible member. A snap stud is fixed to the eyelet shaft on a top side of the electrode.
The eyelet conductivity may be utilized to control the conductivity pattern of the electrode. In that regard, the eyelet head may be formed from an electrically conductive material selected to match the conductivity of the conductive flexible member or a material having a greater or lower conductivity than the conductivity of the conductive flexible member.
In one embodiment of the present invention, the connector may comprise a plurality of spaced apart snap eyelets, each having a head in a contact with the conductive flexible member and a shaft extending through the conductive flexible member and a non-conductive sheet
The plurality of snap studs is provided with one each fixed to each of the plurality of snap eyelet shafts. Thus, the conductivity of the electrode is not only controlled by the material or construction of the eyelet head, but also in the relative spacing of the eyelets from one another and across the electrode. In that regard, each of the plurality of the snap eyelets may have a different conductivity or the snap eyelets may be grouped into sets of snap eyelets with each eyelet in a set having the same conductivity but different from an eyelet conductivity in a different set. These combinations can be utilized to control the current distribution provided to a user and is also a useful for providing specific conductive/current distributions for enhancing drug delivery to a patient.
The conductive flexible member may itself include a conductive film with a conductive ink pattern disposed thereon. Preferably, the ink pattern has a greater conductivity than the conductivity of the conductive film.
In one embodiment of the present invention, the conductive flexible member may comprise a conductive film with a first conductive ink pattern disposed on the member bottom side and a second ink conductive pattern disposed on the member top side. These ink patterns may be utilized in combination with eyelet placement in order to further control the current distribution and conductivity of the electrode. Such ink patterns are shown in U.S. Pat. Nos. 5,904,712, 6,038,455 and 5,843,155. These patents are to be incorporated herewith in their entirety by this specific reference thereto.
In yet another embodiment of a medical electrode in accordance with the present invention, generally includes a conductive flexible member having a top side and a bottom side. A non-conductive flexible sheet covering the conductive flexible top side is provided to prevent inadvertent contact with the conductive flexible member.
A connector provides means for establishing electrical contact with an external electrical apparatus and a conductive tape provides a means for adhering the connector means to the conductive flexible member bottom side. This unique arrangement provides for additional control over the current distribution provided by the medical electrode.
A conductive adhesive adhered to the conductive flexible member bottom side and the conductive tape provides electrical conductivity to a patient""s skin. More particularly, the conductive tape may comprise a conductive backing and a conductive adhesive disposed between the conductive flexible member bottom side and the conductive backing. The conductive backing may comprise any suitable material such as a conductive polymer, a conductive fabric or a metallic foil. The flexibility of the conductive member is, of course, necessary as hereinabove described, and provides a criteria for suitability of the conductive member.
The tape conductive backing and conductive adhesive may have a conductivity less than or equal to the conductivity of the flexible member. On the other hand, the conductive backing and conductive adhesive may have a combined conductivity greater than the conductivity of the conductive flexible member.
In order to control conductivity or current distribution of the medical electrode, the conductive tape may be wider than the conductive means and, in fact, have a shape which provides a means for controlling the overall conductivity of the medical electrode. Controlling elements of the conductive tape also include the thickness of the tape which may be varied. This control over electrode conductivity may, of course, be used in combination with other known methods of controlling conductivity as hereinabove noted in U.S. Pat. Nos. 5,904,712, 6,038,485 and 5,843,156.
A method for making a medical electrode in accordance with the present invention generally includes the steps of providing a conductive flexible member having a top side and a bottom side and disposing a non-conductive flexible cover sheet upon the conductive flexible member top side. A connector is provided for establishing electrical contact with an external electrical apparatus and the method includes adhering the connector to the conductive flexible bottom side with a conductive adhesive tape. Thereafter, a conductive adhesive is applied to the conductive flexible member bottom side and the conductive adhesive tape.